The design of the tread profile for a tire is an important factor in the performance of the tire. For example, when a tire rolls across a surface, the tire is subject to cyclical compressive forces. The design of the tread profile for the tire may have a significant impact on the pressure distributions that are developed in the tire tread due to these compressive forces. Portions of the tread that are subjected to relatively higher contact pressures may fatigue faster than other portions of the tread, thereby resulting in unacceptable performance.
One portion of the tread that may be of concern is the shoulder rib. In many tires, the shoulder rib may have a tendency to wear during typical use. Further, the shoulder rib may be subjected to increased forces when, for example, the tire is turned during use. Specifically, when a vehicle utilizing the tire turns during use, the tread, and specifically one of the shoulder ribs of the tread, may be subjected to suddenly increased forces. Thus, the potential for fatigue and failure of the tire at the shoulder ribs may be one area of concern in the design of tread profiles.
Conventional tread profile designs utilize arcs to define and model the tread profile. For example, a variety of arcs may be formed between the shoulder of the tire or the edge of contact of the tread and the top center point of the tread. The tread profile may be modeled based on these arcs. However, the use of arcs to define and model a tread profile has disadvantages. For example, the curvature of the arcs at the intersections of adjacent arcs may have different curvatures. These varying curvatures may cause difficulties in controlling the pressure distributions at the arc intersections.
In particular, the pressure distributions across the shoulder ribs may be difficult to control when arcs are utilized to define and model a tread profile. For example, FIG. 3 provides a data plot illustrating one example of the pressures across a tire tread formed utilizing arcs. The tire tread formed and tested according to FIG. 3 was designed using five arcs between the top center point of the tread and the intersection between the tread and the sidewall. As illustrated by FIG. 3, the relative pressure distribution along this tread is undesirably high in important areas of the tread. For example, the pressure distribution on the exterior portions of the shoulders ribs may be undesirably high. Specifically, with reference to the X-axis in FIG. 3, the pressures in the region between an axial position of approximately −90 and an axial position of approximately −75, and in the region between an axial position of approximately 75 and an axial position of approximately 90, may be undesirably high.
Therefore, a tread profile and a method for forming the tread profile that helps to control pressure distributions in a tire tread would be useful. Further, a tread profile having a continuous curvature throughout the profile and a method for forming the tread profile would be useful. These and other advantages will be apparent from the description of the present invention that follows below.